Planar transducers (also referred to as speakers) have a film composed of mylar, polyester, kapton, etc, suspended between rows of fixed magnetic bars composed of ceramic, neodymium(a rare earth), etc. Electronic signals carrying the sound to be generated are sent through the wires imbedded in the film. The variable magnetic fields created by the thin wires interact with the nearby fixed magnets to vibrate the film, thereby creating sound waves. They are similar to electrostatic speakers only in that thin film propagates the sound waves. Electrostatics don't use magnets, but create a magnetic field by reciprocating the field back and forth through high voltage stators via a transformer. A planar can handle much more power and produce higher sound pressure levels (SPL). The best version of a planar is a Line Source type. A “Line Source” version planar is narrow in width and very long compared to its width. This produces a cylindrical pattern, yielding enormous lateral coverage and almost no directionality above or below the ends of the driver. They also are very rugged and present an almost purely resistive load to the amplifier. Line source speakers can also handle a lot of power as the relatively large area of film results in a large distribution of the power. Developed many years ago, they have recently become more popular with the advent of high power magnets, durable thin films, advanced adhesives to hold the aluminum traces to the film, sturdier metals for lighter framework, and tensioning techniques. No other speaker design offers the low distortion, excellent coverage, even dispersion, limited ceiling-floor reflections, and high SPL's as does a Planar Line Source.
Higher frequency audio components are more directional, and it has been discovered that in a diaphragm type transducer, it is desirable to have the higher frequency audio sounds emanate from a narrow and long strip like zone or area of the vibrating diaphragm. If the strip transducer is oriented in an upright position, the higher frequency audio sounds will emanate horizontally in substantially all directions resulting in a more uniform distribution of the audio signal. Sound attenuates only 3 dB for each doubling of distance instead of 6 dB as in conventional point source speakers. This provides for more consistent coverage and minimizes lost acoustic power.
Lower audible frequencies on the other hand do not tend to be as directional as the higher frequencies and can either be handled with a planar speaker or a separate more conventional point source speaker with no loss in performance.
U.S. Pat. No. 3,919,499 (incorporated herein by reference) (Nov. 11, 1975) discloses a planar film speaker composed of planar zones where each zone may have a separate circuit for reproducing a different spectrum of the audio signal.
U.S. Pat. No. 4,037,061 (incorporated herein by reference) (Jul. 19, 1977) discloses a mechanical structure which permits a rapid and relatively simple assembly where the tolerances are automatically obtained as a result of the transducer design.
U.S. Pat. No. 3,919,499 (incorporated herein by reference) is believed to be the closest prior art. However, it differs from this invention in that the different line circuits for reproducing different audio spectrum are in separate structures or locations which can require a larger physical structure or result in a larger aperture which may diminish the speaker's “sweet spot” area of audio sound reproduction.